I would make that trade. I just traded LMiller and JMaclin for OBj to free up a roster spot. I feel like I got away with highway robbery. There is a chance I regret giving up Miller, but there is no chance I'll regret picking up OBj.
Houston's defense is not the same - and the team is often playing from behind. The Houston pass offense is bad, Osweiler is absolutely terrible, the 29th worst QB in the NFL (DVOA, terrible accuracy on film) despite targets Hopkins and Fuller. As long as teams have so little to fear in the passing game, they will stack the box against Miller. Houston is never in the red zone. Houston is dead last in offensive DVOA after 5 weeks (they are the least efficient team). Houston has dropped from 6th to 13th in defensive DVOA since the departure of JJ Watt (so they'll be giving up more points and playing from behind). Houston is 31st in special teams DVOA (giving up good field position, not getting good field position). How is Miller supposed to succeed in that scenario?
Freeman is on an offense that is hitting on all cylinders - the OL is in sync, the passing game is a huge threat (wait for Sanu to get more involved) - they are first in offensive DVOA. Freeman is a more natural RB than Coleman and kills it between the tackles. Atlanta is always making it to the redzone. Their defense is middling, so they will be forced to score lots of points, or if their offense takes a huge lead, more carries for Freeman to kill clock. Everything sets up for Freeman. Barring unforseen injury, I don't see how Freeman won't be a consistent producer all year, and I certainly wouldn't regret trying to grab a player in a perfect situation.